1. Field of the Invention (Technical Field)
The present invention relates to substituted piperazine compounds characterized in that the piperazine compounds have a single unsubstituted ring nitrogen, which compounds bind to one or more melanocortin receptors and are agonists, antagonists, mixed agonist-antagonists, or inverse agonists with respect to one or more melanocortin receptors, and use thereof for the treatment of metabolic, immune, infection-related and melanocortin receptor mediated disorders.
2. Background Art
A family of melanocortin receptor types and subtypes have been identified, including melanocortin-1 receptors (MC1-R) expressed on normal human melanocytes and melanoma cells, melanocortin-2 receptors (MC2-R) for ACTH (adrenocorticotropin) expressed in cells of the adrenal gland, melanocortin-3 and melanocortin-4 receptors (MC3-R and MC4-R), expressed primarily in cells in the hypothalamus, mid-brain and brainstem, and melanocortin-5 receptors (MC5-R), expressed in a wide distribution of tissues.
In general, compounds specific for MC1-R are believed to be useful for treatment of melanoma. Compounds specific for MC3-R or MC4-R are believed to be useful in regulation of energy homeostasis, including use as agents for attenuating food intake and body weight gain, for use in treatment of anorexia, as a weight gain aid, for treatment of obesity, and treatment of other food intake and metabolism-related purposes. Compounds specific for MC3-R and MC4-R, among other melanocortin receptors, can further be used as agents for treatment of sexual dysfunction, including male erectile dysfunction. Other melanocortin receptor-specific compounds, such as MCR-1 agonists, can be used as tanning agents to increase melanin production in the skin, acting as chemo-preventive agents against harmful effects of UV solar radiation. Compounds specific for MCR-1 and MCR-3 may further be useful in regulation of inflammatory processes.
There is a significant need for compounds with high specificity for discrete melanocortin receptors, as well as for compounds that are either agonists or antagonists for specific melanocortin receptors. High affinity compounds for melanocortin receptors can be used to exploit varied physiological responses associated with the melanocortin receptors, either as agonists or antagonists. In addition, melanocortin receptors have an effect on the activity of various cytokines, and high affinity compounds for melanocortin receptors can be used to regulate cytokine activity.
There are piperazine and piperidine compounds known, such as those disclosed in WO 02/070511 (Bristol-Myers Squibb Company), WO 02/059095 (Eli Lilly and Company), and WO 00/74679 (Merck & Co., Inc.), asserted to be specific for melanocortin or related receptors. However, in general such compounds have at most two functional substituted groups, wherein each structure is further diversified to make these melanocortin agents. Moreover, these compounds have relatively poor affinity and specificity, and are not suitable for use as a drug compound. Further, none of the piperazine compounds have a single unsubstituted ring nitrogen. There is a significant need for compounds with high specificity for discrete receptors, such as melanocortin and other receptors, as well as compounds that are agonists or antagonists for such receptors. High affinity compounds for such receptors can be used to exploit varied physiological responses associated with the receptors, either as agonists or antagonists. There is thus a need for compounds that are more selective, including higher affinity and specificity that are optimized around a ring structure with at least two to four simple biologically active substituted groups. This invention addresses that need.
WO 02/085925, “Melanocortin Receptor Ligands” (The Proctor & Gamble Company), discloses ketopiperazine structures and methods of synthesis thereof, but does not disclose methods to synthesize piperazine structures, the methods of this invention to synthesize piperazine structures, or methods to synthesize optically pure structures, and further does not disclose piperazine compounds with a substituent group that is a single D-Phe residue, or a derivative or homolog thereof, optionally with an amine capping group. All the compounds disclosed therein differ from the present invention in a number of ways, including that all compounds disclosed have a substituent with a nitrogen-containing heteroatom cationic center.
With respect to certain objects, methods, synthetic schemes, utilities, applications, definitions, protocols and other disclosures, this application is related to U.S. patent application Ser. No. 10/762,079, entitled “piperazine Melanocortin-Specific Compounds”, filed on Jan. 21, 2004; U.S. patent application Ser. No. 10/837,519, entitled “Melanocortin Receptor-Specific Compounds”, filed on Apr. 30, 2004; International Application No. PCT/US02/25574, International Publication No. WO 03/013571, entitled “Peptidomimetics of Biologically Active Metallopeptides”, filed on Aug. 12, 2002; and the specifications of each of the foregoing are incorporated herein by reference as if set forth in full.